Explanation:
Sweeping northward in planet Earth's sky,
comet Machholz
extended its long ion tail with the
Pleiades star cluster
in the background on January 7th.
This stunning view,
recorded with a telephoto lens in
skies over Oberjoch, Bavaria, Germany, emphasizes faint,
complex tail
structures and the scene's lovely blue
and green colours.
Merging with the blue dust-reflected starlight of the Pleiades,
colours in the comet's
ion tail and greenish coma are
produced as gas molecules
fluoresce in sunlight.
Reflecting the sunlight, dust from
comet Machholz trails
along the comet's
orbit
and forms the whitish tail jutting
down and toward the right.
While the visible
coma
spans about 500,000 kilometres,
the nucleus of the comet, likely only a few kilometres
across, lies hidden within.
Comet tails can extend
many millions of kilometres
from the nucleus, but appear substantially shortened
because of perspective.